How to recreate the lighting of a reference illustration, with low sun and pink shades on the mountains
I was able to recreate it with two lights, a (lightly emitting) backdrop, and a very dark, but slightly violet tinted, world.



Breakdown


The lights are Area lamps with a fairly big size (for soft shadows), illuminating from the two sides, slightly towards the horizon. One is bright pink/orange (750W), the other is a slightly less bright (500W) blue/violet. 

An alternative, if you'd like to have more realistic shadows, is a three-light setup, with one sharper, brighter pink light coming from the direction of the sun: see pic below ↓


The world, as you can see, is dark violet (because the ground in the foreground is in a violet shade).
The backdrop is just an image with low relative emission (1.0). Actually I used a mesh plane and circle with a gradient texture.
The ground is just a default principled material with no specularity.


I also used a high focal length (100mm) camera.

Results

(these are based on the two-light setup)

Eevee


Cycles


Note: I picked the backdrop color with the color picker from your reference image, but they appear duller in my render because I used the default Filmic Color Management settings. Depending on the kind of color you want to give to your scene, you might opt for a different color management scheme.

The file

This was created with an alpha version of Blender (2.82), so it may have compatibility issues.